Correlation of early change in SULmax with pCR of breast cancer to neoadjuvant pertuzumab-trastuzumab

There is a need for predictive biomarkers to identify patients with HER2-positive breast cancer who may benefit from neoadjuvant targeted therapy alone. The multicenter phase II trial TBCRC026 evaluated neoadjuvant pertuzumab plus trastuzumab for stage II or III ER-negative, HER2-positive breast cancer. pCR was seen in 22% of patients. The patients underwent ¹⁸F-FDG PET-CT at baseline and day 15 of the first cycle. Between patients who obtained pCR and who did not, a significant difference in median percent reduction of tumor maximum standardized uptake value corrected for lean body mass (SULmax) by day 15 was observed (63.8% versus 41.8%; p=0.004) and SULmax reduction ≥ 40% was more prevalent (83% versus 52%; p=0.03; positive predictive value 31%). Patients not obtaining 40% reduction in SULmax by day 15 were unlikely to obtain pCR (negative predictive value 91%).